<title>New registration technique using voltage-contrast images for low-energy electron-beam lithography</title>

Abstract

We have developed a new registration technique for low energy electron beam lithography. A notable feature of this technique is the use of voltage contrast images caused by charging at the resist surface. Using the electron beam of incident energy range of 1keV to 4.5keV, we detected the mark buried by thick insulator films; even if direct access tot he marks by the primary beam is prevented, the mark detection is possible. The detection time is a few milliseconds, and it is sufficiently fast. We confirmed that this technique is available for various layers of DRAM. Also the possible mechanism that may explain the voltage contrast image caused by negative charging is discussed.